PL166502B1 - Functional liquid - Google Patents

Abstract

1. A drilling mud containing an aqueous surfactant, characterized in that the surfactant is a structured surfactant. PL PL PL

Description

The subject of the invention is drilling sludge containing an aqueous surfactant.

The term "drilling sludge is used herein to refer to liquids used in drilling rock holes to lubricate and cool the drill bit, and to drain rock cuttings from the well face." The term also includes "fracturing fluids that are used to clean the sides of wells prior to cementing." Drilling slurries are used in the production of deep wells and boreholes, as well as special holes in the oil and gas industry. As used herein, the term "drilling sludge also includes" construction sludge which is used in civil engineering and the construction industry to stabilize boreholes and trenches by preventing the slate from collapsing when exposed to water.

The term "electrolyte herein" refers to those ionic compounds which dissociate at least partially in aqueous solution to form ions and which, at the present concentrations, tend to reduce the overall solubility (including nicellar concentration) of surfactants in such solutions by the "salting out" phenomenon. The term electrolyte content or concentration as used herein refers to the total amount of dissolved electrolyte but no solids in the suspension.

The designation "micelle" means either a spherical or rod-shaped particle formed by aggregation of surfactant molecules and having a radius smaller than a second multiple of the average length of the surfactant molecules. The particles in a micelle are typically positioned such that their hydrophilic ("front") groups lie on the surface of the micelles and their lipophilic ("back") groups are located inside the micelle.

The term "bilayer" denotes a surfactant layer approximately two particles thick that is formed from two adjacent parallel layers each containing surfactant particles that are arranged such that the lipophilic portions of the particles are located inside the bilayer. and the hydrophilic portions are located on its outer surfaces. The term "double layer" herein also includes comb-structured layers which are less than two particles thick. The comb-structured layer can be considered as a double layer in which the two layers interpenetrate each other allowing at least some degree of overlap between the back groups of the molecules of the two layers.

The term "spherulite" denotes a spherical or nodular body with dimensions 0.1 µm to 50 µm. Spherulites can sometimes be distorted to an elongated, flattened, pear-shaped, or dumbbell-shaped shape. The term "bubble" denotes a spherulite containing a liquid phase bounded by a bilayer. The term "multiple vesicles" means a vesicle that contains one or more smaller vesicles. Spherulites found in structured surfactant systems are typically concentric multiple vesicles.

The term "lamellar phase" denotes a hydrated solid or liquid crystal phase in which a plurality of double layers are arranged substantially in parallel with an indefinite extent, separated by layers of water or aqueous solution, and having a sufficient regular grid spacing from 25 nm to approximately 150 nm to allow easy detection by neutron scattering or X-ray diffraction when they are present as a significant part of the composition. As used herein, this term does not include concentric multiple bubbles.

The term "G phase" denotes a liquid crystalline lamellar phase of the type also known in the literature as "ordered ** phase" or "lamellar ** phase." The G-phase for each surfactant or mixture of surfactants normally exists in a narrow concentration range. Pure G-phases can normally be identified when examining a sample under a polarizing microscope between crossed polarizers. Characteristic structures are observed according to the classic study of Rosevear, JAOCS Vol. 31 P628 (1954) or J. Colloid and Interfacial Science, Vol. 20 No. 4, P. 500 (1969). G phases are normally characterized by a repeat spacing of 50-70 nm when tested by X-ray diffraction or neutron scattering. "Stretched G phase" means a G phase with a repetition spacing of 110-150 nm.

The term "spherical G-phase" denotes multiple vesicles formed by substantially concentric coatings of the double-layer surfactant alternating with the aqueous phase with a G-phase spacing or an extended G-phase. Typically, conventional G phases may contain a small amount of spherical G phase.

The term "lye" denotes an aqueous electrolyte-containing liquid phase which is separated from a second liquid phase containing a more active ingredient and less electrolyte than the lye phase.

The term "lamellar composition" denotes a composition in which most of the surfactant is present in the lamellar phase or in which the lamellar phase is a major factor in inhibiting sedimentation. The term "spherulitic composition" means a composition in which most of the surfactant is in the form of a spherical G phase or which is substantially stabilized against sedimentation by a spherical G phase.

By the term "structured surfactant" is meant a liquid composition which has a shear dependent viscosity and suspension properties, and which comprises a surfactant intermediate phase, which may optionally be dispersed in or together with the aqueous phase, the aqueous phase is typically the lye phase. The intermediate phase may, for example, contain a G phase, spherulites, especially a spherical G phase, or a lamellar hydrated solid.

By "loading factor **" is meant a water-insoluble, partial mineral with a specific density greater than 3.5 and preferably greater than 4, for example barite or hematite. By the term "drilling sludge" is meant a drilling lubricant that contains mineral particles in suspension, such as rock cuttings or a weighting agent.

The main problem with drilling lubricants is that they most often contain mineral oil, which is a potential pollutant and fire hazard. The present invention addresses this problem through the use of aqueous structured surfactants

Active substances that are better accepted by the environment than mineral oils do not create a fire hazard and yet may have the same or better physical properties and chemical stability.

Oil mining sludge is normally pumped continuously downward through the drill rod through the holes in the drill bit, then is pushed to the surface through the annular space between the drill rod and the well wall to suspend the rock cuttings. At the surface, the drill holes are separated from the drilling sludge which is recycled. Prior to cementing the wellbore, the sludge is replaced with spacer fluid which drains loose particles from the wellbore and leaves a clean, water-wetted surface to ensure good bonding to the cement.

Certain rocks present particular problems when drilling or trenching because of their tendency to break up in the cutting fluid to form a fine grain material that is very difficult to separate from the fluid and that quickly accumulates in the recycle stream, causing an increase in viscosity. The main rock among these problematic rocks is slate, which usually breaks down in the presence of water.

An acceptable drilling lubricant must have a viscosity that is low enough under shear to allow easy flow, but must also have suspended solids. In order to meet these conflicting requirements, a thixotropic liquid is usually needed. Moreover, this liquid must not cause excessive breakdown of rocks such as shale. If it is to be suitable for deep drilling, the liquid must be thermally stable and it is important to avoid excessive loss of liquid in the formation.

Until now, these requirements have almost always been met by the use of either oil or an oil-water emulsion as drilling cutting fluid. The oil coats the slate particles and prevents them from coming into contact with water, thus inhibiting their breakdown. However, this in turn creates environmental problems, especially when drilling into the seabed where rock cuttings are thrown away. To avoid serious environmental contamination, the oil must be separated from the cuttings before it can be discarded. It is very difficult and costly to reduce oil contamination to the currently acceptable level, but even such small residual amounts of oil are ecologically undesirable, and there is an attempt to replace all oil-based drilling lubricants.

The alternative of using aqueous solutions containing polymeric dispersing or suspending agents and / or bentonite to form a slurry containing rock cuttings is less harmful to the environment and may be slightly less expensive than using oil-based sludges, but only for shallow drilling and where the rock formation does not pose any special problems. For deep drilling or drilling or digging in difficult rock formations, such as shale, which is very common in oil mining and trench drilling, such cheap aqueous fluids are unsuitable. They have insufficient thermal stability to withstand the high temperatures in deep rock formations and break down slate. Their lubricating ability is also usually inferior to that of oil-based sludges.

Attempts have been made to improve the properties of aqueous drilling fluids by various special additives such as polymer coating agents and high concentrations of electrolyte to help stabilize the shale. This increased the cost of the sludge considerably, but failed to develop an aqueous liquid with properties capable of replacing oil-based sludge for deep drilling. However, the emphasis on environmental protection is increasing and forcing oil companies to use relatively expensive and technically inferior water-based fluids instead of conventional oil-based sludges.

The art of formulating laundry detergents and similar cleaning preparations is remote from the art of formulating lubricants and hydraulic fluids. The problems to be overcome in both are not similar. However, we have found that in the case of liquid cleaners, it is often necessary to use suspended solids. For example, hard surface scouring creams require the presence of abrasives, and effective laundry detergents require costly, effective fillers.

166,502 active substances which may be poorly soluble or insoluble in water. These problems have been solved by using the interaction between electrolytes and surfactants to form solid dispersion structures based on thixotropic suspensions or mutual suspensions of surfactant intermediate phases with aqueous electrolyte solutions.

United Kingdom Patent No. 2,123,846 describes the use of a platelet surfactant inter-dispersed with an electrolyte solution in a liquid laundry detergent. Another structure, also referred to in United Kingdom Patent No. 2,123,846 and which occurs, although not specifically identified, in formulations exemplified in a number of other publications, comprises an array of spherulites, each having multiple concentric surfactant coatings arranged in alternating with layers of electrolyte solution. Patent descriptions that cite formulations that are likely to exhibit a spherolitic or lamellar structure are as follows:

AU 482374 GB 855679 US 2920045 AU 507431 GB 855893 US 3039971 AU 522983 GB 882569 US 3075922 AU 537506 GB 943217 US 3232878 AU 542079 GB 955081 US 3235505 AU 547579 GB 1262280 US 3281367 AU 548438 GB 1405165 US 3328309 AU 550003 GB 1427011 US 3346503 AU 555411 GB 1468181 US 3346504 GB 1506427 US 3351557 CA 917031 GB 1577120 US 3509059 GB 1589971 US 3374922 CS 216492 GB 2600981 US 3629125 GB 2028365 US 3,638,288 DE A1567656 GB 2031455 US 3,813349 GB 2054634 US 3956L58 DE 2447945 GB 2079305 US 4019720 US 4057506 EP 0028038 JP- -A-52-146407 US 4107067 EP 0038101 JP- -A-56-86999 US 4169817 EP 0059280 US 4,265,777 EP 0079646 SU 498331 US 4,279,786

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EP 0084154 SU 922066 US 4,299,740 EP 0103926 SU 929545 US 4302347 FR 2283951

although in most cases the structures that would exist in the formulations described would be insufficiently stable to keep the solids in suspension. United Kingdom Patent No. 2,153,380 describes a spherulite structure and methods of making a tightly packed, space-filling structure strong enough to withstand various forms of shear and temperature stresses, but mobile enough to be easily poured. This method requires optimization of electrolyte concentrations within strict limits.

In our currently pending UK Patent Application No. 8906234.3 we describe the use of structured surfactants as a carrier for pesticides.

Our pending UK Patent Application No. 891,925 describes methods of obtaining a particulate suspendable surfactant structure in substantially electrolyte free systems.

Hitherto known functional fluids, including oil-based drilling slurries and lubricating fluids, contained minor amounts of surfactants as emulsifiers for the oil or as dispersants for the slurry. Surfactants have typically been substantially monolayers surrounding droplets or particles of oil or solid in a colloidal suspension. The protection of the shale in the drilling sludges has generally been accomplished by having the shale coated with oil. The suspending properties and the thioxotropic nature of the oil-based drilling sludge were provided by the interaction of the dispersed oil droplets. In the case of oil-free sludges, the protection of the shale was ensured by the presence of polymers which irreversibly surrounded the rock particles and were therefore consumed quantitatively in separating the rock. Solids suspending properties are provided by polymeric thickeners such as sodium carboxymethylcellulose or methacrylates. They strive to stabilize the suspension at the expense of fluid mobility.

Electrolytes have been used in both oil-based drilling muds and water-based drilling muds to control water activity. If the electrolyte concentration is high enough to reduce the water activity of the sludge to the same level as the water activity of the shale, then hydration of the shale will not occur. However, if the water activity of the sludge is too low, the slate will tend to dehydrate and become brittle, while if this water activity is too high then the slate will tend to hydrate and break down unless there is some protective barrier between the slate and water factor. Unfortunately, it is not possible to consistently maintain an optimal level of electrolyte because the mineral layers contain soluble salts which tend to dissolve in the sludge, changing the electrolyte content as the sludge passes through the bore.

We have now found that aqueous structured surfactants have surprisingly good lubricating capacity for both rock and metal even at very high pressures and in the absence of very high pressures additives. Moreover, such structured surfactants exhibit the rheological properties required by a drilling lubricant or hydraulic fluid, as well as the ability to absorb solid rock cuttings into slurry or swarf, and surprisingly prevent shale from breaking down even in the complete absence of oil or protective polymer. We believe that slate is protected by coating it with a surfactant. The liquid is easily separated from the drill holes and any residual surfactant can be easily flushed out of the drill holes with water. The clean cuttings pose no ecological hazard and can be safely thrown away. Water

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- the surfactant is a structured surfactant, such as those formed by the interaction of the surfactant with a dissolved electrolyte, preferably in a spherulytic system. Typically it is an aqueous surfactant intermediate phase inter-dispersed with the aqueous continuous phase or the aqueous electrolytic continuous phase.

An important and particularly surprising property of spherulitic compositions when used as drilling cutting fluids is the low loss of formation fluid, which is significantly less than with conventional drilling cutting fluids, even without additives that are normally needed. The structured surfactants can be easily formulated in a thermally stable form for high temperature applications such as deep drilling.

In our invention, both the suspending properties and the protection of the shale are provided essentially by a surfactant, preferably in combination with some dissolved electrolyte. While we do not wish to limit this, we do believe that the surfactant can reversibly coat the shale particles. It can also help maintain optimal water activity. The surfactant is preferably present in our composition as a spherical G-phase, a dispersed plate phase or micelles.

The invention makes it possible to drill wells by using a water-based, structured surfactant as a drilling or cutting fluid, which is preferably a solution containing surfactant micelles or interdispersed with a lamellar solid, spherolitic or G-phase surfactant. in an amount sufficient to prevent shale decay or to provide protection against abrasion of the metal surface and to keep the rock cuttings in suspension under normal drilling conditions.

The drilling sludge containing the aqueous surfactant of the invention comprises structured surfactant as surfactant.

The slurry according to the invention comprises solid particles of shale and / or a loading agent suspended therein.

The sludge according to the invention is suspended particles of barite and / or hematite.

The sludge according to the invention comprises as structured surfactant (A) an aqueous phase and (B) a lamellar solid, a spherulytic phase or a G phase dispersed or inter-dispersed with said aqueous phase, and contains an electrolyte solution as the aqueous phase.

According to the invention, a part of the electrolyte solution may be brine, and sea water may be used as the brine.

The slurry according to the invention comprises graphite particles in suspension.

The slurry according to the invention preferably contains 5-45% by weight of surfactant. The surfactants may constitute up to about 35% by weight of the sludge, although it is preferable for both economic and rheological reasons to use lower concentrations, e.g. less than 30%, usually less than 25%, preferably less than 20%, e.g. 10-15% by weight .

The surfactant may, for example, consist essentially of an at least sparingly water-soluble salt of a sulfonic acid or a monoesterified sulfuric acid, for example an alkylbenzene sulfonate, an alkyl sulfate, an alkyl ether sulfate, an olefin sulfonate, an alkane sulfonate, an alkyl phenol sulfate, an alkyl phenol ether sulfate, alkyl ethanolamide sulfate, ether sulfate alkyl ethanol amide, or alpha-sulfo fatty acid or esters thereof, each with at least one alkyl or alkenyl group of 8-22, typically 10-20 aliphatic carbon atoms. The alkyl or alkenyl groups mentioned are preferably straight chain primary groups, but may optionally be secondary groups or branched chain groups. The term "ether" herein refers to oxyalkylene groups and homogeneous and mixed polyoxyalkylene groups such as polyoxyethylene, polyoxypropylene, glycerin, and polyoxyethylene-oxy mixed groups.

166 502 propylene or mixed glycerine-oxyethylene, glycerin-oxypropylene, or glycerin-oxyethylene-oxypropylene groups, typically containing from 1 to 20 oxyalkylene groups. sodium dodecyl dimethyl benzene sulfonate, sodium lauryl sulfate, sodium tallow sulfate, potassium oleyl sulfate, monoethoxy ammonovolauryl sulfate, or 10 mole ethoxylate monoethanolamine cythyl sulfate.

Other anionic surfactants useful in the present invention include fatty alkyl sulfosuccinates, fatty alkyl ether sulfosuccinates, fatty alkyl sulfosuccinates, fatty alkyl ether sulfosuccinates derivatives, acyl sarcosinates, acyl taurates, isentionates, soaps, oleates, linoleates, and linoleates rosin soaps and alkyl ether carboxylates and saponates. Anionic phosphate esters, including naturally occurring surfactants such as lecithin, may also be used. In any case, the anionic surfactant comprises at least one aliphatic hydrocarbon chain of 8-22, preferably 10-20, usually an average of 12-18 carbon atoms, an ionizable acid group such as a sulfo group, sulfuric acid group, carboxy group, phosphonium group or a phosphoric acid group and, in the case of ethers, one or more glycerol groups and / or 1-20 ethyleneoxy groups and / or propyleneoxy groups.

The preferred anionic surfactants are sodium salts. Other salts of industrial interest are the salts of potassium, lithium, calcium, magnesium, ammonium, monoethanolamine, diethanolamine, triethanolamine, and alkyl amines containing up to seven aliphatic carbon atoms, for example isopropylamine.

The surfactant preferably comprises or consists of nonionic surfactants. The nonionic surfactant can be, for example, a C10-22 alkanolamide with a mono or dialkanolamine of a lower order, such as monoethanolamide or coke or tallow diethanolamide. Other nonionic surfactants that may optionally be used include ethoxylated alcohols, ethoxylated carboxylic acids, ethoxylated amines, ethoxylated alkylamides, ethoxylated alkylphenols, ethoxylated glycerol esters, ethoxylated sorbic acid esters, ethoxylated phosphate and propoxylated esters, butoxylated and mixed ethoxylated analogs propoxy and / or butoxy of all the aforementioned ethoxylated nonionic agents, all bearing a Ce-22 alkyl or alkenyl group, and up to 20 ethyleneoxy and / or propyleneoxy and / or butyleneoxy groups, or any other nonionic surfactant that has been used so far in powdered or liquid detergent compositions, for example amine oxides. The latter typically have at least one Ce-22 alkyl or alkenyl group, preferably C10-20, and up to two lower order alkyl groups (for example C1-4, preferably C1-2).

Preferred nonionic agents for the purposes of the invention are, for example, those having the HLB range of 2-18, for example 8-18.

The slurries of the invention may contain cationic surfactants which include fourth order amines having at least one long chain (e.g. C12-22, typically C16-20) alkyl or alkenyl group, optionally one benzyl group, and as the remaining four substituents short chain alkyl groups (such as example C1-4). Also included are imidazolines and quaternary imidazolines having at least one long chain alkyl or alkenyl group and amidoamines, and quaternary amidoamines having at least one long chain alkyl or alkenyl group. All quaternary surfactants are usually anion salts which impart some degree of solubility in water, such as formate, acetate, lactate, tartrate, chloride, metasulfate, ethosulfate, sulfate or nitrate. Cationic surfactants having two long chain aliphatic alkyl groups, for example tallow groups such as bis-tallowyl quaternary ammonium and imidazole salts, are particularly effective as lubricants.

The sludges of the invention may also contain one or more amphoteric surfactants, which include betaines, sulfobetaines, and phosphobetaines formed by reacting a suitable tertiary nitrogen compound having a long chain.

An alkyl or alkenyl group with a suitable reagent such as chloroacetic acid or propane sulfone. Examples of suitable tertiary nitrogen-containing compounds include: tertiary amines having one or two long chain alkyl or alkenyl groups and optionally a benzyl group, the other substituent being a short chain alkyl group; imidazolines having one or two long chain alkyl or alkenyl groups, and amidoamines having one or two long chain alkyl or alkenyl groups. Typically, amphoteric surfactants are less preferred than nonionic or anionic surfactants.

The types of surfactants described above are only examples of the more general surfactants suitable for use in the present invention. Any surfactant can be used. A more complete description of the main types of surfactants that are commercially available is given in "Surface Active Agents and Detergents" by Schwartz, Perry and Berch.

In general, the surfactants to be used according to the invention should preferably be substantially non-toxic, especially for marine life, and should be substantially stable at temperatures above 100 ° C, preferably above 120 ° C, especially above 150 ° C, e.g. for deep drilling applications. - above 180 ° C.

Dissolved electrolytic compounds are very preferred components of the composition. While it is possible to prepare structured surfactants without electrolyte if the concentration of the surfactant is high enough, the mobility of such systems is often insufficient unless the surfactant is selected with great care. The addition of an electrolyte enables the preparation of mobile structured surfactants with a relatively low concentration of surfactant.

Suitable electrolytes include the water-soluble alkali metal, ammonium and alkaline earth metal salts derived from strong inorganic acids. Particularly preferred are the sodium and potassium salts, especially the chloride. However, lithium, calcium and magnesium salts can also be used. Among the salts that are useful, there may be phosphates, nitrates, bromides, fluorides, concentrated phosphates, phosphonates, acetates, formates, and citrates. It is often particularly advantageous in the case of drilling fluids to form a composition by diluting the surfactant concentrate in situ with natural brine (e.g., seawater in the case of drilling into the seabed). The brine may be all or part of the electrolyte contained in the drilling fluid.

The electrolyte may be present up to saturation. Typically, the lower the surfactant content, the more electrolyte will be required to form a structure capable of carrying solids. It is preferable to use higher concentrations of electrolyte and lower concentrations of surfactant, and to choose the cheapest electrolytes for economic reasons. The electrolyte should normally be present in a concentration of at least 0.1% by weight based on the total weight of the composition, usually at least 0.5% by weight, for example more than 0.75%, preferably more than 1%. Typically the concentration is less than 30%, more usually less than 10%, for example less than 8% by weight. Typically the concentration is in the range 1-5%.

The maximum electrolyte concentration depends, inter alia, on the type of structure and the required viscosity, as well as on cost considerations. It is preferable to formulate spherulitic compositions as described in GB-A-2, 153,380, in order to obtain a satisfactory balance between mobility and high levels of solids in suspension. The optimal electrolyte concentration for each specific type and amount of surfactant can be ensured, as described in the above-mentioned patent application, by measuring the change in electrical conductivity with increasing electrolyte concentration until a first conductivity minimum is observed. Samples can be prepared and tested by centrifugation for 90 minutes at 20,000 g, adjusting the electrolyte concentration to obtain a suspending agent that does not separate into two phases during centrifugation.

Preferably, the electrolyte concentration is adjusted so as to obtain a composition that does not sediment when left for 3 months at ambient temperature or at 0 ° C or 40 ° C. Compositions that do not show signs of sedimentation or separation are preferred

166 502 into two or more layers after being kept for 72 hours at 100 ° C in an autoclave. Preferably also the electrolyte concentration is adjusted so as to obtain a shear stable composition and one that is desired which does not significantly increase in viscosity when left under normal shear action.

Alternatively, sufficient electrolyte may be added to form a plate pattern as described in British Patent No. 2,123,846, for example by adding an amount of electrolyte sufficient to ensure that the liquid suspending agent separates on centrifugation at 800 g after 17 hours, forming a lye phase. containing little or no surfactant. The amount of water in the formulation can then be adjusted so as to obtain the optimal balance between mobility and stability.

In the case of drilling slurries and spacer fluids, it is usually desirable to provide the wellbore with a fluid that contains the necessary concentration of surfactant and electrolyte to form a structure that allows the suspension of solids. However, salts found in the rock in which the drilling is performed can sometimes be able to form this structure in situ, as long as an aqueous surfactant is provided. It is often advantageous to provide a water system containing a less than optimal amount of electrolyte to allow the minerals present in the wellbore to dissolve.

The amount of electrolyte needed also depends on the nature and solubility of the surfactant. Typically, high cloud point surfactants require less electrolyte than low cloud point surfactants. With some surfactants, no electrolyte is needed at all.

The surfactants or mixtures of surfactants that can be used in the electrolyte-free compositions of the present invention are typically those that form a G phase at ambient temperature, but preferably do not form an M1 phase. Generally speaking, the aqueous surfactant has a cloud point of greater than 30 ° C, typically greater than 40 ° C, and preferably greater than 50 ° C. Aqueous surfactants with a cloud point above 60 ° C are especially useful. Alternatively or additionally, the surfactant may have an inverse cloud point below 30 ° C, more usually below 20 ° C, especially below 10 ° C, preferably below 0 ° C. Surfactants with an inverse cloud point below -10 ° C are especially preferred. Reverse cloud points are typical of some nonionic surfactants where increasing temperature tends to break the hydrogen bonds responsible for the hydration of the hydrophilic part of the molecules, making it less soluble. Normal cloud points are more typical of anionic or cationic surfactants. Mixtures of anionic and non-anionic surfactants may exhibit cloud point and / or reverse cloud point.

Usually it is preferred that the surfactant is present in a concentration of at least 1%, for example at least 3% by weight of the composition, more usually greater than 5%, especially greater than 8% and preferably 10-15%. A typical range of surfactant concentrations is from 6 to 15%, more usually 7-12%. Another concentration of surfactants that can be used is 1-30%, for example 2-15% by weight. The concentration of the surfactant should preferably be sufficient in the presence of any electrolyte in the formulation to form compositions with a plastic viscosity as measured by a Fanna viscometer of 5-35 cP i.e. 0.0050.035 Pa s, preferably 0.015-0.03, e.g. 0, 02-0.025 Pa · s. Preferably the composition should have a yield point greater than 7.25 Pa, more preferably 14-25 Pa, especially 17-22 Pa, for example 20 Pa. It is especially preferred that the composition has a yield stress to plastic viscosity ratio of 50 to 120, especially 70-95, for example 85.

A surfactant concentration above 60% is possible but very unlikely for industrial use at least in most of the envisaged applications of the invention.

Particularly preferred in electrolyte-free systems are nonionic and mixed nonionic surfactants, especially mixtures of aliphatic alcohol ethoxylates, and mixtures of aliphatic alcohol ethoxylates with fatty acid ethoxylates.

166 502 or mixed ethoxylate / propoxylated alcohols, and fatty acid ethoxylates. For example, mixtures containing one or more C10-C20 aliphatic alcohols and / or fatty acids alkoxylated with 5-10 ethyleneoxy and / or propyleneoxy groups are particularly useful. Other nonionic surfactants that can be used include alkoxylated alkylphenols, alkoxylated amines, alkoxylated sorbic or glycerol fatty acid esters, and alkanolamides such as coconut mono or diethanolamide, and mixtures thereof.

Drilling slurries contain suspended solids which may be cuttings such as shale and / or may contain a weighting agent such as barite or hematite. The total amount of solids in the slurry may typically range from about 5% by weight to about 60% by weight, or more preferably 10-50%, such as 35-45%.

Preferably, sufficient amount of loading agent is used to obtain a specific gravity of 1-1.8.

The drilling slurry may optionally contain a suspending agent such as carboxymethylcellulose or polyvinyl pyrrolidone, typically in amounts up to 5%, for example 0.5-2% by weight. For reasons of cost and rheology, however, it is preferable to avoid the use of such suspending aids.

The drilling muds according to the invention are preferably substantially free of oil or organic solvents or also water-miscible solvents, such as low-order mono or polyhydroxy alcohols, ketones and polyethers, or water-insoluble solvents such as aromatic hydrocarbons, and also free of any hydrotropes. such as urea, benzene sulfonate or lower order alkyl benzene sulfonates. Solvents and hydrotropes tend to interfere with the structuring of the surfactant, and require the use of much larger amounts of surfactant and / or electrolyte. They also increase the cost of the formulation without significantly improving the properties. Moreover, oil and solvents are highly undesirable for environmental reasons. If used at all, it is preferred that the oils, solvents and hydrotropes are present in an amount of less than 10%, more preferably less than 5%, most preferably less than 1%, for example less than 0.5%, usually less than 0.1%. %, most often less than 0.05% by weight of the composition weight.

It is preferred that there are no polymeric thickeners such as resins at all, or that they are present in concentrations of less than 5%, preferably less than 0.5%, as they are not normally needed to stabilize the composition and increase costs. and the viscosity of the suspension.

The drilling slurries or other functional fluids of the invention may optionally contain auxiliary structuring agents such as bentonite, but such additives are not normally required to prevent fluid loss and may be detrimental to rheological properties. If used, the bentonite should preferably not constitute more than 5% of the total weight of the composition. However, the drilling lubricants of the present invention will usually suppress the presence of bentonite incidentally derived from minerals in the wellbore.

Drilling slurries may optionally contain graphite in suspension to increase lubricity.

The composition may optionally contain a biocide such as glutaraldehyde or preferably a tertiary phosphonium hydroxymethyl salt such as THP sulfate or a mixture thereof with glutarin aldehyde to inhibit the growth of sulfate reducing bacteria that can cause pipe corrosion, liquid stratification, and / or formation contamination.

Lubricants may contain high pressure additives, and all of the functional fluids of the invention preferably contain corrosion inhibitors such as phosphite esters, phosphonates, polyphosphonates, chromates and zinc salts. The corrosion inhibitors are preferably organic chelating agents or other inhibitors of corrosion caused on the surface of metals by aqueous solutions.

The invention will be further illustrated in the Examples, where all percentages are by weight of the total weight of the composition, unless otherwise stated.

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Example 1 2 3 4 5 AES 3.2 3 2.65 - - IPABS 6.4 7 4.02 - - LABS - - 10.7 10.7 AO - - 2.1 2.1 DEABS - - 2.1 2.1 KC 1 - 1 1.2 1.0 KA 0.4 - - - Yield point N m- ² 35.43 24.42 18.19 6.22 4.79 Plastic viscosity Pa · s 0.015 0.043 0.021 0.025 0.02 GP / LP X10 ' ³ 23.62 5.58 6.66 2.49 2.4 Loupe recovery at room temperature 94.8 96.2 97.8 95.8 91.2 Slate recovery at 60 ° C - 92.0 93.2 91.8 87.0

AES - sodium C12-aikyl-3 mol-ethoxy sodium sulfate,

IPABS - isopropylamine C10-14-lime alkyl benzene sulfonate,

LABS - sodium C10-14-linear alkylbenzene sulfonate,

AO - C12-18 alkyl dimethyl amine oxide,

DEABS - diethanolamine-C10-4alkylbenzene sulfonate,

KCl - potassium chloride,

KA - potassium acetate.

Examples 1, 2 and 3 were clear micellic solutions. Examples 4 and 5 were opaque spherulite compositions.

All five examples were capable of slurrying 50 g of barite in 350 ml at 80 ° C for 18 h.

Example 6. Drilling slurry was prepared by slurrying 1118.7 g of barite in 1500.0 g of 10% aqueous IPABS. The latter was an opaque spherulite composition and the formed sludge was a stable suspension.

Example 7 Drilling sludge was prepared by slurrying 1028.8g of barite and 3g of silicone antifoam in 1500g of an aqueous spherulite composition containing 2.25% diethanolamine, 10.5% LABS, and 2.25% amine oxide.

Example 8. Drilling sludge was prepared by slurrying 1094.6 g of barite, 37.5 g of bentonite and 3 g of silicone antifoam in 10% aqueous IPABS.

Example 9. A drilling mud suitable for use in seabed drilling using seawater contains 8% LABS, 8% coconut diethanolamide and 4% sodium chloride.

Example 10. The products of Examples 6, 7 and 8 were compared to a commercial oil based sludge for sedimentation using the inclined tube test. The drill pipe, 1 meter long and 40 mm in diameter, containing the tested sludge and set at an angle of 45 ° to the vertical, was left for 120 h, at the end of this period, separation of the less opaque phase was visible in the upper 35 cm zone of the oil-based sludge, while the desired separation was not seen in the samples of the invention.

Example 11. A commercial oil-based sludge was compared to the products of Examples 6 and 7 for low pressure static filtration. This indicates the tendency of the sludge to lose formation fluid. The results are given in Table 1.

Table 1

Oil based sludge (comparative) Example 6 Example 7 The thickness of the filter cake 1 mm <1 mm <1 mm The obtained filtrate 3.5 ml 3.6 ml 1.7 ml

Example 12. The lubricity of the composition described in Example 9 was tested using the FALEX method described in Institute of Petroleum test method IP 241 69.

The blank metal roller was rotated between the two V-shaped pieces with a gradually increasing load, and the roller was immersed in the tested lubricant without circulation.

166 502

The sludges according to the invention were compared with three comparative lubricants, viz. Water, mineral oil and a bentonite suspension. All three comparisons failed (2.2 kN, 4.5 kN and 6.7 kN, respectively). In contrast, the composition of the invention showed excellent lubricity at all loads, including a maximum load of 17.8 kN. Only this lubricant out of all four survived the test without damage.

Example 13. Various structured surfactants were compared to water, mineral oils and unstructured surfactant solutions in the test of Example 12. The results are summarized in Table 2, all percentages being weight percent of the total weight of the mixture. The lubricants are listed in order of improving properties. Only the last three lubricants survived the entire test without seizure.

Table 2

Lubricant Coefficient of friction 1 Damage 1 2 3 4 x i Water 0.107 7 s at 3.3 kN x ii.Mineral oil containing additives for high pressures ("Tellus R10) 0.065 44 s at 3.3 kN x iii. Mineral oil without additives (Turbo T68) 0.048 6s at 5.6 kN x iv. 30% LABS (no structuring) 0.050 45 s at 6.7 kN v. Example 1 from British Patent 2,123,846 (lamellar structure) 0.048 54 s at 6.7 kN vi. 14% LABS 6% ESR (spherulitic) 0.042 13 s at 0.9 kN vii.10% IPABS (Spherulite) 0.038 45 s at 11.2 kN viii. 3% IPABS, 12% AES, 4% NaCl (spherulite) 0.063 41 s at 12.2 kN ix. 12% LABS, 8% AE, 3% NaCl (spherulite) 0.031 41 s at 15.5 kN x.50% IPABS (phase G) 0.024 57 s at 17.8 kN xi. 8% LABS, 8% coconut diethanolamide, 4% NaCl (spherulite) 0.024 51 s at 19 kN xii. 8% LABS, 8% coconut diethanolamide, 4% NaCl 2% graphite (spherulite) 0.027 51 s at 19 kN xiii. 20% LABS, 10% coconut diethanolamide (spherulite) 0.028 no damage at 20 kN xiv. 3% LABS, 12% IPABS, 2% NaCl (spherulite) 0.026 no damage at 20 kN xv. 25% imidazolin ² (spherulitic) 0.020 ^M U

x Comparative example,

1. Coefficients of friction measured just before damage / end of test,

2. 1-Methyl, 1-tallowamidoethyl, 2-tallium-imido azoline methosulfate.

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Claims (10)

Patent claims Claims 1. Drilling slurry containing an aqueous surfactant, characterized in that it comprises structured surfactant as the surfactant. 2. The sludge according to claim The process of claim 1, characterized in that it comprises solid particles of shale and / or a loading agent suspended therein. 3. The sludge according to claim The process of claim 1, comprising suspended solid particles of barite and / or hematite. 4. The sludge according to claim A process as claimed in claim 1, characterized in that the structured surfactant comprises (A) an aqueous phase and (B) a lamellar solid, a spherulite phase or a phase (G) dispersed w / or inter-dispersed with said aqueous phase. 5. The sludge according to p. The process of claim 4, wherein the water phase is an electrolyte solution. 6. The sludge according to claim The process of claim 5, wherein at least part of the electrolyte solution comprises brine. 7. The sludge according to claim The process of claim 6, wherein the brine is sea water. 8. The sludge according to claim 1 The process of claim 1, wherein the suspension comprises solid graphite particles. 9. The sludge according to claim 1 The composition of claim 1, comprising 5-45 wt.% Surfactant, based on the total weight of the sludge. 10. The sludge according to claim 1 A method according to claim 1, characterized in that it contains a sufficient amount of dissolved electrolyte to form, with said surfactant, a stable spherulite or plate composition capable of taking up a solid in suspension.